Puntastic quirky goodness! Excellent, fun to read, informative article. Those piezo transducers, could probably benefit from a little pre-amp tickle, before being fed into that absurdly overkill Fender head and speaker cabinet. Ha... I like it!

I agree completely that it's always best to refer to data sheets (when possible), and do precise calculations to determine the optimal component values. I'm sure your more exacting explanation will be helpful to many. Thanks for taking time to put it together.

Is that a twinge of sarcasm I detect? If the purpose of this article were to demonstrate what is being switched, rather than the method of switching, said load would certainly have been the focus, and included in the diagrams. I'll leave judgement about the "real world" validity of what I've shared up to each individual creative minded reader, rather than the "world-at-large". Thanks for sharing your existential "tip" though.

Ah, yes, that is indeed an important trait of reed relays that I will include in the next edit of the article, after the judging for the contest concludes. Thanks for pointing out one of the things that I didn't think of mentioning.

Your interest, and vote are appreciated. I assume you're referring to reed contacts being sealed in glass, so not exposed to air, therefore less likely to arc when switching higher voltages?

The coil will certainly be less stressed because it wont heat up. The mechanical wear may be reduced slightly, because the permanent magnetic field may reduce the friction at the switch armature pivot point. The switch contacts will be susceptible to the same deterioration though.

Here's an example of how to get a rough calculation for the resistor value. For a 12V relay with a coil resistance of 280 ohms, 12/280 = .043. So the coil will draw about 43mA. 2/3 of which is about 30mA. 12/.03 = 400, so the nearest standard resistor value is 390 ohms. A 1/4W resistor should be okay, but if it gets hot use one rated at 1/2W. A 1000 microfarad capacitor should work for most applications. Make sure to select a capacitor with a voltage rating slightly above your supply. Ultimately you will probably need to try different values until you find what works for your application.

I appreciate your comment, and your vote. If you use this technique, please come back and share how it works out for you.

All of the automobiles that I've worked on to date still use electromagnetic starter solenoids. I'm not aware of any auto manufacturers using solid-state switches in place of them. It would take some beefy transistors to handle the massive current required to spin a conventional starter motor. Thanks for checking out my article, and for taking time to comment. Also, thanks for pointing out that relays are still extensively used in automitive applications.

Thanks for your interest in my article, and for taking time to comment. Using a magnet to make a standard relay latch, was something that I discovered through playing around. The driver circuit is an adaptation of a design I found in a web post several years ago. That circuit was intended as an alternative way to drive a single coil latching relay without using an H-bridge. It used a single low gain transistor, which needed a relatively low value base bias resistor, which determines the holding current of the circuit. I was inspired to experiment with modifying the design, the goal being to reduce the holding current to the max. The original circuit required a holding current somewhere in the low milliamps range. The Darlington pair transistor arrangement that I've used has so much gain...

Thanks for your interest in my article, and for taking time to comment. Using a magnet to make a standard relay latch, was something that I discovered through playing around. The driver circuit is an adaptation of a design I found in a web post several years ago. That circuit was intended as an alternative way to drive a single coil latching relay without using an H-bridge. It used a single low gain transistor, which needed a relatively low value base bias resistor, which determines the holding current of the circuit. I was inspired to experiment with modifying the design, the goal being to reduce the holding current to the max. The original circuit required a holding current somewhere in the low milliamps range. The Darlington pair transistor arrangement that I've used has so much gain that the circuit will work with even higher value base bias resistors. I tested the circuit with a 10 Mohm resistor and it still works, but it causes the capacitor to discharge more slowly, which creates a delay of a few seconds before the relay can be actuated again.

I'm glad you found my article useful. I'm not sure if there are IC drivers on the market that offer similar characteristics. I doubt there are any with the same exact functionality and ultra low holding current spec.

The combined look of skulduggerous menace, and Teslaesque control apparatus, appeals to my affinity for turn-of-the-century tech, and heavy-metal band accoutrements.An aha moment struck me a while back and I coupled an LED to an LDR. Delightful experimentation ensued. It seemed inevitable that this component already existed, but until reading your article, I was unaware of the vactrol. Thanks for that satisfying bit of info.